day 16: aaaaaaaaaaaaaa

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xenia 2020-12-16 00:31:34 -05:00
parent ef930612d7
commit 8674bc7d56
1 changed files with 84 additions and 0 deletions

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16.rkt Normal file
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#lang curly-fn racket
(require "scripts/aoc.rkt")
;; solution for day 16
(struct note [name rule0 rule1] #:transparent)
(define (invalid? notes val)
(not
(for/or ([n (in-list notes)])
(match-define (note name (cons a b) (cons c d)) n)
(or (and (>= val a) (<= val b)) (and (>= val c) (<= val d))))))
(define (part1 input)
(match-define (list notes yours others) input)
(for/sum ([tick (in-list others)])
(for/sum ([val (in-list tick)] #:when (invalid? notes val)) val)))
(define (part2 input)
(match-define (list notes yours others) input)
(define (ticket-valid? tick)
(not (for/or ([val (in-list tick)]) (invalid? notes val))))
(define valid-tickets (filter ticket-valid? others))
(define mapping (make-hash))
(for ([idx (in-range (length yours))])
(define decided-note (mutable-set))
(for ([cand-note (in-list notes)])
(define shonks
(for/and ([tick (in-list valid-tickets)])
(not (invalid? (list cand-note) (list-ref tick idx)))))
(when shonks
(set-add! decided-note (note-name cand-note))))
(when (set-empty? decided-note) (error "couldn't decide..."))
(hash-set! mapping idx decided-note))
; (displayln mapping)
(let loop ()
(for ([(k v) (in-hash mapping)])
(when (= 1 (set-count v))
(define fst (set-first v))
(for ([k2 (in-list (hash-keys mapping))] #:unless (= k2 k))
(set-remove! (hash-ref mapping k2) fst))))
(when (for/or ([(k v) (in-hash mapping)])
(> (set-count v) 1))
(displayln "looping")
(loop)))
(displayln mapping)
(for/product ([val (in-list yours)] [idx (in-naturals)])
(define n (set-first (hash-ref mapping idx)))
(displayln n)
(if (string-contains? n "departure")
(begin (displayln val) val)
1)))
;; parse input file
(define (parse fname)
(match-define (list notes yours others) (string-split (file->string fname) "\n\n"))
(define sn string->number)
(define pnotes (for/list ([line (in-list (string-split notes "\n"))])
(match line
[(pregexp #px"^([^:]+): (\\d+)\\-(\\d+) or (\\d+)-(\\d+)$"
(list _ name a b c d))
(note name (cons (sn a) (sn b)) (cons (sn c) (sn d)))])))
(define pyours (map sn (string-split (second (string-split yours "\n")) ",")))
(define pothers (for/list ([line (in-list (rest (string-split others "\n")))])
(map sn (string-split line ","))))
(list pnotes pyours pothers))
(module+ test
(require rackunit)
;; tests here
(displayln "no tests :("))
(module+ main
(define input (parse "inputs/16"))
(answer 16 1 (time (part1 input)))
(answer 16 2 (time (part2 input)))
(displayln "meow"))